1. Technical Field
The present disclosure generally relates to the field of catheters and devices that are inserted intravascularly for the purpose of medical treatment, and more particularly, to a device that increases safety during cardiac lead extraction procedures.
2. Description of the Related Art
Cardiac lead extraction is a procedure that is performed to properly manage patients with cardiac rhythm devices. Traditionally, the indications for removing implanted cardiac leads have resulted from infections caused by cardiac rhythm devices. More recently, these indications have expanded to include the removal of redundant leads, maintaining vascular access for upgrading devices, and the removal of recalled pacemaker and defibrillator leads. As a result, there is an increasing need for cardiac lead extraction procedures.
Cardiac lead extraction procedures are also required because cardiac leads are not lasting as long as desired due to increased patient longevity. In addition, as cardiac rhythm devices have increased in complexity, there is a need to upgrade such devices from single or dual chamber to biventricular pacers or implantable cardioverter-defibrillators (ICDs). This procedure involves adding additional leads through a patient's subclavian vein. The subclavian vein, however, can be occluded, thereby making cardiac lead placement impossible without removing the old leads and opening a channel. Lead extraction procedures may also be performed with mechanical and laser sheaths. The need for such sheaths is due to the formation of adhesions around a patient's veins over a period of time.
Referring now to FIG. 1, a perspective view of a heart and vessels with an implanted cardiac lead are presented. A cardiac lead 10 is seen to traverse from the left subclavian vein (not shown in Figure) into the left innominate vein 40, then into the right atrium 60, and through the tricuspid valve into the right ventricle 70. A lead extraction sheath 20 is advancing over cardiac lead 10 into the intravascular space. A cardiac lead tip or electrode is presented at a right ventricular apex 80 and adjacent to a left ventricle 90. One of the feared complications of a lead extraction procedure is a tear 52 at a superior vena cava 30 and a right atrial 60 junction that can result from traction and the use of laser sheaths or other energy sources. This complication results in the need for immediate open chest surgery to repair the tear 52. Due to sudden blood loss, hemodynamic collapse typically occurs and despite immediate open heart surgery, the patient may not survive. In anticipation of this feared complication, most physicians performing lead extraction prepare patients for possible open heart surgery. For example, it is typical for a cardiac surgeon to be available in the operating room as the cardiologist or cardiac electrophysiologist is performing the procedure in the event a vascular tear occurs.
Currently, there are no known methods to non-invasively prevent or treat a defect such as tear 52 at the superior vena cava 30 and right atrial 60 (SVC-RA) junction. Moreover, there are some cases involving patients that may be considered high risk for lead extractions. For example, certain patients demonstrate excessive scarring in the region of the SVC-RA junction but there is no known method to pre-determine this disposition. Specifically, patients demonstrating excessive scarring may be at higher risk for vessel injury and tear. It is generally accepted that cardiac leads that have been in place for many years pose an increase risk during extraction. It is also accepted that patients who have not had prior cardiac surgery can be at risk due to lack of adhesions around the heart that may otherwise limit or contain bleeding, if a tear were to occur. Other high risk categories include patients with multiple leads. Unfortunately, despite pre-operative risk assessment, complications still occur. The incidence of this particular complication is about three to four percent of all cases and in many cases the patient does not survive. The risk of death is generally reported to be about 0.4% of all cases.
Several techniques are presently utilized to prevent and treat vascular tears. For example, endovascular stenting is used to reopen narrowed vessels and to treat damaged vessels, such as in the case of endograft treatment for an aortic aneurysm. In another example, covered stents are used to patch or cover vascular tears using an endovascular approach. Although these stents work by direct apposition and contact with the vessel wall, the desired effect to treat damaged vessels is not achieved and external bleeding typically occurs as a result of poor stent to vessel wall contact. Similarly, in cases of lead extraction, if a covered stent is used, it may be deployed in different methods. For example, a stent may be passed over a wire and deployed in such a manner that the cardiac lead is external to the stent and sandwiched between the stent and vessel wall. In this case, there is poor stent to vessel contact and bleeding continues.
There is significant variability in instances in which leads are in contact with or scarred into the vessel wall. Due to these drawbacks, endovascular stenting may not be feasible. For example, stents are generally rigid and non-flexible. As a result, the complexity of anatomy involving the innominate vein, SVC and right atrium makes it difficult to achieve good stent apposition while maintaining blood flow to the heart. In addition, a user can no longer proceed with the lead extraction procedure because the lead is now trapped between the stent and vessel wall.
Another method is to position a covered endovascular stent through a wire passed through the lead extraction sheath. In this case, it is possible that a user may deploy the stent in such a manner that the cardiac lead is inside the stent and not outside. However, with this approach, difficulties arise because the stent may not be deployable as a result of adhesions, presence of multiple cardiac leads, or incomplete lead removal. Furthermore, in cases of right ventricular perforation, this method is ineffective.
Therefore, a need exists to allow cardiac lead extraction procedures to be performed with increased safety.